Modern T Handle Knob 5/16 Male Thread

When a knuckle is gone and you have no insert screw to substitute, you'll be glad you have an extra one of these.

This is one of those little items that you don't realize makes your life easier until it's missing. Very common for knobs to go missing, do yourself a favor and buy 3 or 4 of these so you are always ready if one disappears. They come in a variety of thread sizes, so double check which size you need before ordering.